petMD Blogs

The Daily Vet is a blog featuring veterinarians from all walks of life. Every week they will tackle entertaining, interesting, and sometimes difficult topics in the world of animal medicine – all in the hopes that their unique insights and personal experiences will help you to understand your pets.

In my years of veterinary practice, I haven’t felt an overwhelming urge to test my patients to determine the exact nature of their breed mix. Overall, I’ve not observed a trend where being of a specific breed designates an unwavering certainty that a particular illness will occur.

Instead, a stronger correlation seems to exist between a pet’s size (i.e., small, medium, large, and giant for dogs) and the potential for a certain disease to occur. For example, small dogs tend to have having poor periodontal health, while large dogs are commonly afflicted by orthopedic conditions.

Yet knowing my patients’ breed combinations can spur the awareness of unique disease conditions that are known to affect a particular breed. For example, herding breeds like the Australian Shepherd, Collie, Shetland Sheepdog, and others may have a defect in the multi-drug resistance gene (MDR1) which yields an increased likelihood that adverse reactions to medications may occur. What are these medications? Well, there’s quite a variety, including:

Antiparasitics — ivermectin, milbemycin, etc.

Antidiarrheals — loperamide (Immodium), etc.

Anticancer agents — doxorubicin, vinctristine, etc.

Fortunately for the dogs that could be negatively impacted by the administration of these drugs, the Veterinary Clinical Pathology Lab at Washington State University offers a blood or cheek swab test to determine if a defect in the MDR1 gene exists.

Recently, I had a client seeking clarity on the mix of breeds that went into creating the composite that was her family’s new canine companion. From a standpoint of care provision, knowing if my patient had a defect in the MDR1 gene would lend valuable insight as to whether he could show an adverse reaction to the above mentioned drugs.

This was the first time I received such a request, so I pursued some guidance from experts at the Veterinary Information Network (VIN) as to their recommendation for a test that was touted to be the most reliable. Subsequently, I ordered a MARS Wisdom Panel Insights test and collected a sample from my patient.

Fortunately, just a small quantity of cells from the inside of a dog’s cheek is needed. Collection requires that either pet owner or care provider use the provided wire brush (like that used to clear a drainage pipe) to swab the inside of the patient’s cheek for a period of at least 30 seconds. In an impatient and squirmy puppy, this can present somewhat of a challenge.

Once our sample was collected, it was placed in a convenient postage-paid envelope and shipped back to the manufacturer. A few weeks later, we had our results.

The Wisdom Panel® Insights computer algorithm performed over seven million calculations using 11 different models (from a single breed to complex combinations of breeds) to predict the most likely combination of pure and mixed breed dogs in the last 3 ancestral generations that best fit the DNA marker pattern observed in (my patient).

So, what did my patient turn out to be? It turns out he’s a blend of Alaskan Malamute mixed breed and Australian Koolie mixed breed. Further, his grandparents were also combinations of Alaskan Malamute mixed breed and Australian Koolie mixed breed.

There are some likely contenders making up the mixed breeds that contributed to the genetic material. The MARS report explained …

We have identified for you the 5 next best breed matches which appeared in the analysis of your dog's DNA. One or more of these breeds could have contributed to the genetic makeup of the ancestors indicated by the mixed breed icon. The breeds are listed by the relative strength of each result in our analysis with the most likely at the top of the list. There could also be a breed or breeds present in the mixed breed component that we cannot detect with our current database of purebred dogs.

So, my patient’s top five include:

1. Finnish Spitz, 8.33%

2. Golden Retriever, 7.77%

3. German Shepherd Dog, 7.27%

4. Afghan Hound, 4.85%

5. Catahoula Leopard Dog, 3.16%

So he is part Catahola Leopard Dog after all. At least his mix of breeds does not put him on the list of candidates potentially suffering health problems as a result of the MDR1 gene defect.

What do you think about genetic testing to determine what breeds compose a mixed breed dog?

Thank you for your comments.
Yes, there does exist a test for the defective MDR1 gene.
http://www.vetmed.wsu.edu/depts-VCPL/index.aspx
Some of the veterinary oncologists I work with also will run this test in order to determine a pet's potential sensitivity (i.e. intolerance) to certain chemotherapy drugs.
Dr. PM

Thank you for your comments.
Yes, certainly it with the potential for our next breed dogs to have varying genetic make up's, knowing what combinations of genes could potentially be involved can both satisfy one's curiosity and provide general health information.
Dr. PM

It is very interesting indeed. I have heard anecdotal reports of these tests having questionable reliability - same dog tested more than once has come up with different results each time. The MARS test recommendation is helpful.

As a trainer, I tend to rely more on behavior and movement to improve my guess-timation on the breed in front of me. I teach tracking and odor detection, where breed traits are helpful to know in order to organize the best methods for success. Most important is motivation - what does this dog want, and what might it likely do to get what it wants? A dog that prefers to search with its eyes (most herding/guardian breeds) will learn to use its nose if the visual is hidden and the only option to reach the object of its desire is scent, we need to have that object be something really special. For scent-oriented breeds (scent hounds and most hunting breeds) the desire is built into the search, and the reward is secondary. This is highly significant for trainers. One size does NOT fit all. This is one reason that purebred or purpose bred dogs make the most reliable working dogs, and why so few shelter dogs are successful in search and recovery work. It can happen, of course, but most handlers who provide their own dogs stack the deck in their favor by choosing dogs carefully from knowledgeable breeders. Unfortunately, mixed breed dogs, and dog breeds that the trainer is unfamiliar with, can wash out of the process more than is necessary. I have seen how this happens - falls upon that old saying "if the only tool you have is a hammer, EVERYTHING looks like a nail." Trainers in law enforcement, for example, are more familiar with herding and working breeds, and their training protocols are geared towards using only one 'motivation' - either a ball or tug reward. Give these guys a bloodhound, and sell it on the basis of its superior scenting ability, and you may not have success with the standard training methods. Good luck with getting a bloodie to work for a ball . . . ;-) The good news is these hound breeds usually work out in spite of the lack of interest in toys, because they are hard wired to follow their nose, but the trainer needs to understand breed traits in-depth in order to get the most out of the process.

Things like DNA markers for health risks are good to know, but there is more to this knowledge, more to gain. In my experience, the staff at most animal shelters are not terribly knowledgeable about dog behavior, least of all specific breed behavior traits, and rely almost exclusively on appearance to identify the mix. The common wisdom - I do mean common - is that dog breeds are based on appearance, primarily. But that is putting the sock on inside out. Dog breeds - with a few exceptions - were developed to do a job, behavior, foremost. The appearance comes along for the ride in the basic canine world. It can be said that appearance has a purpose, and in many ways is part of the intended job . . . to show off the owner's status, to be small enough to carry, to have a warm coat, to look intimidating, all for one, one for all. The National Geographic Magazine Feb. 2012 has an amazing series on dog breeds, I highly recommend it, it should be required reading for anyone dealing with canines: http://ngm.nationalgeographic.com/2012/02/build-a-dog/ratliff-text

It's also interesting that you used appearance to determine the mix of breeds with mixed results. If these DNA tests continue to improve, I can see how they can give vets and trainers and pet owners valuable information. Right now, they seem a little frivolous, don't you think? Better would be tests for specific issues, which actually exist in most breeds already. My breed has done extensive work in health issues, to our great advantage. We have reduced the incidence of hypothyroidism - one of the most common health issues in dogs - to below the general canine population average.

It would be wonderful if experts can freely share the knowledge gained over years of observation of dogs - right now there is noticeable resistance to this learning. I don't know why for sure, but I suspect that many people in the shelter and rescue world are offended by breeders in general, and tend to downplay, pooh-pooh the reasons why people might prefer a purebred or purpose bred dog to a roll of the dice at a shelter.

Thank you for your comments.
It's great to hear that you have contributed to the reduction of hypothyroidism in your dog's breed (which was what?). It is probably one of the most common endocrine abnormalities of pets and seems to be so multifactorial in its incidence (obesity, chronic inflammation/infection, occurring secondary to medications/toxins, etc. Are all correlated).
Thank you for the link to the National Geographic article.
Dr. PM

Dr. Patrick, the breed is PBGV. I am not certain of the details behind the hypothyroid stats - since I am not a breeder, I have not done research from that end, but as a working dog handler, I care about health trends, and attend seminars at our national specialty shows, couple of noteable ones with Dr. Dodds and Dr. Jerold Bell. PBGVs are a CHIC breed. Wish I could be more help.

There does seem to be a link between early spay/neuter and hypothyroidism, also hemangio-sarcoma. Not only was my first PBGV hypothyroid by age 4, she died of hemangio-sarcoma at age 11 years and 11 months.

Thank you for clarifying the dog breed.
I'm sorry to hear about the health issues affecting your first PBGV. Hopefully, with good breeding and wellness practices, these diseases will be less common/severe in future generations of the breed.
Dr. PM